In hand-held electronic programmable calculators, it is well known to use one or more external memory modules for an extension of memory capacity or for storing an applications program in a case where a basic program is permanently stored in a ROM. In the calculator system as described above, if the memory module containing a RAM is backed up by a battery for preserving the contents stored in RAM, the RAM may be used as the memory module for storing the applications program in place of using ROM. However, if a RAM is used for storing the applications program as mentioned above, there exists the possibility that the applications program stored in RAM may be erroneously deleted at the time of execution of the initialization program of the system when power is first turned on.